Meanwhile, over 50 governments have called on the UN Security Council to refer the conflict in Syria to the International Criminal Court to investigate war crimes, which have allegedly been committed by both sides in the conflict.

The signatories included many European governments as well as Libya and Tunisia.

But the Council is unlikely to support the move. It is deeply divided over Syria.

Permanent Security Council members China, Russia and the United States are not members of the ICC and have already indicated they would not sign the petition.